A composite metal-cementitious core-metal sandwich typically comprises two metal sandwiching plates with a core of a cementitious material sandwiched therebetween. This is a more effective use of metal as thinner metal plates may be used to achieve a similar load carrying capacity, in particular bending capacity, compared to a metal panel of equivalent metal thickness but that does not have a sandwiched core therein. This is because the sandwiched core can act integrally with the sandwiching plates to increase the leverage between the tension and compression areas of the metal plate in bending, while the sandwiching plates confine the cementitious core in compression, thereby increasing its load carrying capacity. This metal-cementitious core-metal sandwich panel typically has structural applications in the construction of structural decks and hulls of marine vessels and as ice belts in offshore structures.
To form the sandwich, the cementitious core is commonly pre-cast as a panel using dismantleable and removable casting formwork, followed by bonding a metal plate to each face of the resulting cementitious panel after removal of the formwork. Alternatively, the metal plates may be assembled to define a core cavity therebetween, followed by casting the cementitious material into the cavity, with the metal plates acting as formwork for encasing the cementitious material during casting.
Such sandwich panels, although ideal for use in a wide range of structural applications, are vulnerable to interfacial slip between the metal and cementitious core and local buckling of the metal plate under loading because of the naturally poor bonding between cementitious core and metal plates. To overcome this, interfacial bonding agents such as chemical adhesive have been introduced to bond the metal plates to the cementitious core. However, the traditional production process for this is time consuming because the cementitious core has first to be pre-cast in a separate formwork, and it involves costly processes to achieve a void-free and uniform adhesive interfacial layer.
Alternative sandwich structures have been proposed that introduce overlapping metal shear studs or connectors provided on the metal plates and projecting into the core cavity prior to casting the cementitious material into the cavity around the metal studs or connectors. Another version involves connectors welded at both ends to the sandwiching metal plates, and casting cementitious material into the core cavity. Although this can halt interfacial slip and minimize shear failure, buckling of the metal plates away from the cementitious core at locations remote from the metal studs or connectors can still occur because of a lack of a continuous bond between the metal plates and the cementitious core.